The Preventive Defense Project (PDP) is a research effort directed by former Secretary of Defense William J. Perry. Preventive Defense is a concept for U.S. defense strategy in the post-Cold War era, premised on the belief that the absence of an imminent, major, traditional military threat to American security presents today's leaders with an unaccustomed challenge and opportunity to prevent future Cold War-scale threats to international security from emerging. While the U.S. defense establishment continues to deter major regional conflicts and provide peacekeeping and humanitarian relief missions when necessary, its highest priority is to contribute to forestalling developments that could directly threaten the survival and vital interests of American citizens.

To this end, the Project focuses on forging productive security partnerships with Russia and its neighbors, engaging an emerging China, addressing the lethal legacy of Cold War weapons of mass destruction (WMD), and countering WMD proliferation and potential acts of catastrophic terrorism. Through intense personal interaction with political and military leaders around the world, the Project nourishes a highly informed but non-governmental "track-two" dialogue that explores opportunities for international innovation, agreement and cooperation. In doing so, PDP seeks to devise creative new policy approaches that reflect a preventive defense posture. The Project also examines the U.S. government's structural capacity to deal with security challenges at the start of the 21st century.